Release v1.9.4

• [FIXED] read-the-docs template is not compatible with latest sphinx version (7.0.0)
  see readthedocs/sphinx_rtd_theme#1463
• [FIXED] issue #511
• [FIXED] issue #508
• [ADDED] some classes that can be used to reproduce exactly what happened in a previously run environment
  see grid2op.Chronics.FromOneEpisodeData and grid2op.Opponent.FromEpisodeDataOpponent
  and grid2op.Chronics.FromMultiEpisodeData
• [ADDED] An helper function to get the kwargs to disable the opponent (see grid2op.Opponent.get_kwargs_no_opponent())
• [IMPROVED] doc of obs.to_dict and obs.to_json (see #509)